1. Field of the Invention
The present invention relates to the automatic measurement of audio presence and level by direct processing of an MPEG data stream.
2. Description of the Related Art
Digital television, such as that provided by DIRECTV®, the assignee of the present invention, is typically transmitted as a digital data stream encoded using the MPEG (Motion Pictures Experts Group) standard promulgated by the ISO (International Standards Organization). MPEG provides an efficient way to represent video and audio in the form of a compressed bit stream. The MPEG-1 standard is described in a document entitled “Coding of Moving Pictures and Associated Audio for Digital Storage Media at up to about 1.5 MBit/s,” ISO/IEC 11172 (1993), which is incorporated by reference herein.
DIRECTV® broadcasts hundreds of channels to its subscribers encoded into different MPEG data streams. However, problems can arise in using these different MPEG data streams, due to the fact that it is difficult to monitor the audio levels of all of the different channels. Thus, the different MPEG data streams may appear to be either too loud or too soft, as compared to other channels, or there may be a loss of audio that is not noticed for some time.
In the prior art, special purpose devices would be used to measure audio levels. However, these special purpose devices require a separate satellite receiver to tune and decode the audio. In addition, these devices generally are not easily integrated into a system architecture in order to control and report and alarm on the measurements.
Consequently, there is a need to monitor the audio levels of an MPEG data stream. Moreover, there is need for the ability to monitor audio levels of MPEG data streams without decompressing the audio data within the MPEG data streams.